Method and device for preventing plaque formation in coronary arteries

ABSTRACT

A method and device for preventing plaque build-up in a coronary artery includes providing an electrical field generating device, and generating an electrical field in the coronary artery to prevent plaque build-up in the coronary artery. The method further includes sensing the heart rhythm and generating the electrical field after a depolarization wave in the heart. The electrical field is generated by circuitry, in one embodiment implanted circuitry, connected to leads which are epicardially or intracardially positioned on the heart.

FIELD OF THE INVENTION

[0001] The present method relates generally to prevention of plaqueformation in arteries and, more particularly, to application ofelectrical fields to prevent plaque formation in coronary arteries. Thepresent invention also relates to devices for applying electrical fieldsto prevent plaque formation in arteries.

BACKGROUND

[0002] Atherosclerosis is a common disease of the arteries in whichfatty material, cholesterol, and other substances, are deposited on thevessel wall, resulting in narrowing and eventual impairment of bloodflow through the vessel. Larger accumulations are called atheromas orplaques. The fatty material can eventually erode the wall of the artery,diminish the elasticity of the artery, and interfere with the bloodflow. Clots may form around the plaque deposits, further interferingwith blood flow. Severely restricted blood flow to the heart muscleleads to symptoms such as angina or chest pain. In such severe cases,treatments are administered to ensure adequate blood flow to the heart.Conventional treatments, including surgery and medications, attempt totreat the plaque after it has adhered to the vessel wall. Surgicaltreatments include coronary artery bypass grafting, stent implantation,and balloon angioplasty. Medications may be given to controlcholesterol, blood pressure, and abnormal heart rhythms in an attempt tolessen the effects of the plaque buildup in the coronary arteries.However, such treatments are not always effective in preventing the moreserious complications of atherosclerosis, for example, sudden death bylethal arrhythmia, acute myocardial infarction (MI or heart attack), orunstable angina.

[0003] Accordingly, there is a need to provide a method and a device forpreventing plaque formation in coronary arteries.

SUMMARY OF THE INVENTION

[0004] The present method includes generating an electrical field at thecoronary artery, which electrical field acts to slow, and/or prevent,plaque build-up in the coronary arteries. In one embodiment, an implantis inserted into a patient and a lead is positioned adjacent thecoronary artery. The implant generates electrical current carried by thelead, which produces the electrical field in which the coronary arteryis immersed. In another embodiment, the electrical signals andelectrical fields are non-excitatory so that the application thereofdoes not effect the rhythm of the heart.

[0005] A system for reducing and/or preventing plaque build-up in acoronary artery includes an implant having a power source, electricalsignal generating circuitry, and leads connected to the electricalsignal generating circuitry. The leads apply the electrical field forpreventing plaque build-up in the coronary arteries. In one embodiment,the leads include electrodes which are spaced apart from one another incoronary veins. The electrodes produce an electric field, which preventsplaque buildup in coronary arteries which are in the electrical field.

[0006] Other aspects of the invention will be apparent on reading thefollowing detailed description of the invention and viewing the drawingsthat form a part thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the drawings, like numerals describe substantially similarcomponents throughout the several views

[0008]FIG. 1 is a schematic drawing illustrating generally oneembodiment of a system according to the present invention and anenvironment in which it is used.

[0009]FIG. 2 is a schematic drawing illustrating another embodiment ofthe present invention.

[0010]FIG. 3 is a schematic diagram illustrating an implant.

DETAILED DESCRIPTION

[0011] In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the spirit and scope of thepresent invention. The following detailed description is, therefore, notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims and their equivalents.

[0012]FIG. 1 is a schematic drawing illustrating, by way of example, oneembodiment of a medical device for applying an electrical field toprevent and\or reduce plaque build-up in a coronary artery or vein. Thedevice includes an implant 20 positioned within a human body 10. Leads22 are electrically and physically coupled through a multiple portsocket 24 to housing 30. Leads 22 are epicardial leads each having atleast one electrode 25 positioned epicardially on heart 26. Theelectrodes 25 are patches or meshes placed over an area of a coronaryvessel (artery or vein) 36 having an onset of plaque build-up or an areawhere it is believed plaque build-up may begin. The patch or mesh typeelectrodes 25 apply the electrical field to the coronary vessel and, inparticular to the area of the coronary vessel having the onset of plaquebuild-up or the area having a high risk of plaque build-up. Theelectrical field at the artery reduces the adhesion of plaque to thevessel wall and thus reduces the chance of developing atherosclerosis.In some embodiments, the coronary vessel is a coronary artery. In oneembodiment, additional leads 22 are provided to provide further coverageof the heart. In another embodiment, the leads 22 each include aplurality of electrodes 25 such that heart 26 is essentially covered byelectrodes and most of the coronary arteries are positioned within anelectric field to prevent plaque build-up.

[0013] The implant 20 includes the main housing 30 in which a powersource and electrical signal generating circuitry are encased andhermetically sealed suitable for implantation in a body cavity. Housing30 is a metal or metal alloy construction, e.g. titanium or titaniumalloy, or other biocompatible housing materials. The power source andcircuitry will be explained in greater detail below. In one embodiment,the electrical field is produced between the electrodes 25 and thehousing 30. In another embodiment, the electrical field is producedbetween electrodes 25. In yet another embodiment, each electrode patch25 includes at least one anode and cathode for producing the electricalfield.

[0014]FIG. 2 shows another embodiment of the medical device forpreventing plaque build-up in coronary arteries. A single lead 22 is atleast partially intracardially positioned within a cardiac vein 32. Thelead 22 includes at least one electrode 34, here shown as twoelectrodes, which receives an electrical signal and generates anelectrical field which transmits through the wall of vein 32 and entersartery 36. The electrical field at the artery reduces the adhesion ofplaque to the artery wall and thus reduces the chance of developingatherosclerosis. In the embodiment with two electrodes 34, theelectrical field is generated between the two electrodes such that someof the current passed therebetween passes through the coronary artery.It will be understood that a plurality of intracardial leads 22 could beattached to implant 20 and positioned within a plurality of veins 32 toprevent plaque build-up in a plurality of coronary arteries 36 that aresubjected to the electrical field produced by electrodes 34.

[0015] In some embodiments, the leads include the characteristics of theleads described in U.S. Pat. Nos. 6,212,434; 6,178,356; 6,152,954;6,148,233; 6,129,749; 6,097,986; and 5,871,529, all assigned to theassignee of the present application and all incorporated by referencefor any purpose.

[0016]FIG. 3 shows another embodiment with the medical device forpreventing plaque formation or build-up in coronary arteries beingintegral with a cardiac rhythm management device 100. Cardiac rhythmmanagement devices 100, which can be internal or external devices,provide therapy to a patient's heart to correct various forms ofarrhythmia, such as tachyarrhythmias and bradyarrhythmias. Examples ofcardiac rhythm management devices include pacemakers, defibrillators,and devices with combinations of both pacing functions anddefibrillating functions. Device 100 includes a power source 300, anatrial sensing circuit 305, an atrial therapy circuit 306, a ventricularsensing circuit 310, a ventricular therapy circuit 320, and a controller325.

[0017] Atrial sensing circuit 305 is coupled by atrial lead 110A toheart 26 for receiving, sensing, and/or detecting electrical atrialheart signals. Such atrial heart signals include atrial activations(also referred to as atrial depolarizations or P-waves), whichcorrespond to atrial contractions. Such atrial heart signals includenormal atrial rhythms, and abnormal atrial rhythms including atrialtachyarrhythmias, such as atrial fibrillation, and other atrialactivity. Atrial sensing circuit 305 provides one or more signals tocontroller 325, via node/bus 327, based on the sensed atrial heartsignals. Such signals provided to controller 325 indicate, among otherthings, the presence of atrial fibrillation.

[0018] Atrial therapy circuit 306 provides atrial pacing therapy, asappropriate, to electrodes located at or near one of the atriums ofheart 26 for obtaining resulting evoked atrial depolarizations. In oneembodiment, atrial therapy circuit 306 also providescardioversion/defibrillation therapy, as appropriate, to electrodeslocated at or near one, or both, of the atriums of heart 26, forterminating atrial fibrillation and/or other atrial arrhythmia.

[0019] Ventricular sensing circuit 310 is coupled by ventricular leads110B, 110C to heart 26 for receiving, sensing, and/or detectingelectrical ventricular heart signals, such as ventricular activations(also referred to as ventricular depolarizations or R-waves), whichcorrespond to ventricular contractions. Such ventricular heart signalsinclude normal ventricular rhythms, and abnormal ventricular rhythms,including ventricular tachyarrhythmias, such as ventricularfibrillation, and other ventricular activity, such as irregularventricular contractions resulting from conducted signals from atrialfibrillation. Ventricular sensing circuit 310 provides one or moresignals to controller 325, via node/bus 327, based on the receivedventricular heart signals. Such signals provided to controller 325indicate, among other things, the presence of ventriculardepolarizations, whether regular or irregular in rhythm.

[0020] Ventricular therapy circuit 320 provides ventricular pacingtherapy, as appropriate, to electrodes located at or near one of theventricles of heart 26 for obtaining resulting evoked ventriculardepolarizations. In one embodiment, ventricular therapy circuit 320 alsoprovides cardioversion/defibrillation therapy, as appropriate, toelectrodes located at or near one, or both, of the ventricles of heart26, for terminating ventricular fibrillation and/or other ventriculartachyarrhythmias.

[0021] Controller 325 controls the delivery of therapy by ventriculartherapy circuit 320 and/or other circuits, based on heart activitysignals received from atrial sensing circuit 305 and ventricular sensingcircuit 310. Controller 325 includes various modules, which areimplemented either in hardware or as one or more sequences of stepscarried out on a microprocessor or other controller. It is understoodthat the various modules of controller 325 need not be separatelyembodied, but may be combined and/or otherwise implemented, such as insoftware/hardware. In an embodiment, the controller 325 includes amemory in which is stored default parameters and a processor which usesthe parameters stored in memory and sensed data to control varioustherapies.

[0022] In general terms, sensing circuits 305 and 310 sense electricalsignals from heart tissue in contact with the catheter leads 110A-C towhich these sensing circuits 305 and 310 are coupled. Sensing circuits305 and 310 and/or controller 325 process these sensed signals. Based onthese sensed signals, controller 325 issues control signals to therapycircuits, such as atrial therapy circuit 306 and/or ventricular therapycircuit 320, if necessary, for the delivery of electrical energy (e.g.,pacing and/or defibrillation pulses) to the appropriate electrodes ofleads 110A-C. Controller 325 may include a microprocessor or othercontroller for execution of software and/or firmware instructions. Thesoftware of controller 325 may be modified (e.g., by remote externalprogrammer) to provide different parameters, modes, and/or functions forthe implantable device 100 or to adapt or improve performance of device100.

[0023] In one further embodiment, one or more sensors, such as sensor330, may serve as inputs to controller 325 for adjusting the rate atwhich pacing or other therapy is delivered to heart 26. One such sensor330 includes an accelerometer that provides an input to controller 325indicating increases and decreases in physical activity, for whichcontroller 325 increases and decreases pacing rate, respectively.Another such sensor includes an impedance measurement, obtained frombody electrodes, which provides an indication of increases and decreasesin the patient's respiration, for example, for which controller 325increases and decreases pacing rate, respectively. Any other sensor 330providing an indicated pacing rate can be used.

[0024] Device 100 further includes a plaque prevention circuit 350 whichis connected, via node/bus 327, to controller 325. Plaque preventioncircuit 350, in response to control signals from controller 325,generates electrical signals transmitted by lead 22 to electrodes 25 or34. In one embodiment, controller 325 powers the plaque preventioncircuit 350 after a depolarization wavefront (P-waves or R-waves) issensed by one of atrial sensing circuit 305 or ventricular sensingcircuit 310. The controller 325 is programmed to link the activation ofplaque prevention circuit 350 to either the atrial or the ventriculardepolarization so that the electrical field produced by the signal fromcircuit 350 does not interfere with the heart's natural rhythm or arhythm induced by the pacing functions of device 100. The circuit 350 isthus energized during the refractory period of the heart rhythm.Consequently, the device including cardiac rhythm management functionsand plaque build-up prevention functions produces both excitatorysignals (atrial and ventricular therapy circuits 306 and 320) andnon-excitatory cardiac signals (plaque prevention circuit 350).

[0025] The plaque prevention circuit 350 limits the frequency and theenergy in the plaque prevention electrical field. In one embodiment, thefrequency is limited to less than the low end of a normal heart raterange. For example, the frequency of plaque prevention signals islimited to a low rate such as one pulse every 10 seconds or one pulseper minute. In another embodiment, the frequency is about 30 to 60pulses per minute. In some embodiments, the pulse frequency is lass thanabout 1.5 Hz. In some embodiments, the pulse frequency is less thanabout 1 Hz. Limiting the frequency of the plaque prevention signalsreduces the chance of interfering with the rhythm of the heart whilestill reducing plaque build-up in the coronary arteries within theplaque prevention electrical field. On another embodiment, the energy inthe electrical field is less than the electrical energy of a heartstimulation signal. Limiting the energy (current and\or voltage) in theelectrical field prevents the electrical field from stimulating heartmuscle and interfering with heart function. That is, the electricalfield while not capture the heart tissue and dictate a heart rhythm.Moreover, limiting the energy in the electrical field minimizes itseffect on the life of power source 300.

[0026] Power source 300 is a chemical battery providing electrical powerto device 100 for operating the controller 325, powering sensor circuits305, 310, and 330, powering pacing and defibrillation therapiesadministered, as needed, by atrial therapy circuit 305 and ventriculartherapy circuit 320. Power source 300 further powers the plaqueprevention circuit 350 to generate electrical fields for prevention ofplaque build-up in coronary arteries.

[0027] While the above describes one embodiment of a medical device withwhich the teachings herein may be performed, it is recognized that otherembodiments of implantable medical devices may be used. In someembodiments, the teachings described herein are used in conjunction withthe medical devices described in at least one of U.S. Pat. Nos.6,216,035; 6,212,428; 5,891,175; 5,876,424; 5,843,136; 5,800,471;5,792,183; 5,700,283; and 5,632,766, all assigned to the assignee of thepresent application and all are incorporated herein by reference for anypurpose.

[0028] The illustrated embodiments in FIGS. 1-3 schematically show thepositioning of leads 22 and electrodes 25 and 34. Some specificlocations of the electrodes may yield more plaque prevention thanothers. It should be noted, however, that no anatomy is precisely thesame and the positioning may not yield as good as a result for oneperson as compared to another. One specific positioning of electrodes isplacing one lead and electrode in the anterior vein and placing anotherlead and electrode in the lateral vein. The electrical signal isproduced between the two electrodes and a non-heart-excitatory signalpasses through the left marginal artery and the anterior interventricalartery. Other positions of electrodes and leads are within the scope ofthe present disclosure.

[0029] A brief description of one embodiment is provided to morecompletely portray the method and device from preventing plaque build-upin coronary arteries. The device 100 is implanted into the body cavity10, with atrial lead 110A electrically connected to the atrium andventricular leads 110B and 110C respectively electrically connected tothe left and right ventricles. Plaque prevention lead 22 is epicardiallyplaced on heart 26 over a coronary artery 36. The coronary artery 36 hasthe beginnings of plaque formation or is a suspected location for futureplaque formation. The controller 325 receives various inputs fromsensors 330 and sensing circuits 306 and 320, and based on these inputsprovides, as needed, pacing signals and defibrillation signals throughleads 110A-110C. Controller 325 controls operation of plaque preventioncircuit 350, which provides a non-excitatory electrical signal to lead22. Lead 22 transmits the electrical signal to electrode 25, whichcreates an electrical field at coronary artery 36. The electrical fieldcreated by electrode 25 includes a low voltage, low current electricalsignal which at least partially flows through the coronary artery 36.Low voltage is less than four volts in one embodiment and less thanthree volts in another embodiment. The electrical field preventsformation or reduces growth of plaque on the wall of the coronaryartery.

[0030] The present description uses the phrase “electrical field” todescribe the phenomena which prevents plaque build-up in the coronaryartery. One form of the electrical field is current flowing from oneelectrode to another electrode or to the housing of the implant. It isbelieved that the current blocks the fatty material, cholesterol, andother substances from adhering to the arterial wall and to othersubstances already adhered to the arterial wall. The electrical field,consequently, prevents formation of or addition to plaques in theartery.

[0031] In some embodiments, the signals applied by the present device toprevent plaque build-up in arteries include those signals described inU.S. Pat. No. 6,201,991 issued to Chekanov on Mar. 13, 2001, which isherein incorporated by reference.

[0032] In some embodiments, the signals applied by the present devicefor the prevention of plaque buildup in coronary arteries includesadjusting the signal strength to provide a stronger signal during therefractory period and a lower strength signal during the non-refractoryperiod. For example, a typical pacing signal pulse width is about 0.5milliseconds. The signal has a potential of about 0.5 volt if it isapplied to a lead having a good contact, e.g. low resistance and highconductivity, to the patient's tissue. In situations where the contactis poor, then the signal has a potential of greater than 0.5 volt tocompensate for the poor contact. In some embodiments, the signalpotential is about 1 volt. In some embodiments, the signal potential isabout 1-2 volts. In some embodiments, the signal potential is about lessthan or equal to about 10 volts. In some embodiments, the signalstrength applied to the heart tissue is about 0.5 volts or less forpacing. It is desirable to not interfere with the heart's natural rhythmor a paced rhythm while using the present device to prevent plaquebuild-up. Accordingly, the signal strength for the prevention of plaquebuildup is limited to the signal strength applied by a cardiac rhythmmanagement circuit.

[0033] The present device is not so limited during the refractory periodof the heart rhythm. In some embodiments, higher strength signals areapplied during the refractory period. That is, signals for theprevention of plaque buildup may exceed the pacing voltages. The signalsfor prevention of plaque buildup, in an embodiment, exceed 10 volts.Such a signal is directed to the location where it is desired to preventplaque buildup and not directed to the heart tissue whereat such asignal could capture the heart rhythm.

[0034] The present method and apparatus is described in applicationsinvolving implantable medical devices. However, it is understood thatthe present methods and apparatus may be employed in unimplanted medicaldevices. Moreover, while a method and system to prevent plaque build-upin coronary arteries is described above, it is within the scope of thepresent invention to apply the method and system to prevent plaquebuild-up in coronary veins as well.

CONCLUSION

[0035] The device according to the present disclosure positionselectrodes adjacent coronary arteries to produce electrical fields whichprevent or reduce growth of plaque build-up in the arteries. Theelectrodes are positioned epicardially on the heart or intracardially ina coronary vein. The electrodes are adjacent the coronary arteries inneed of plaque build-up prevention. The electrical fields produced bythe device do not excite the heart so as to not interfere with the heartrhythm. In one embodiment, the device includes elements for sensingheart depolarizations and elements for controlling heart function. Thedevice may provide its non-excitatory signals at a very low rate (onesignal per 10 seconds or one signal per minute). In one embodiment, theelectrical field is generated by passing a low current between twoelectrodes with some of the current passing through the coronary artery.The epicardial electrodes are positioned spaced from each other on theheart. The intracardial electrodes are positioned in one vein or theelectrodes are positioned in different veins. In sum, non-excitatoryelectrical fields are provided to prevent plaque build-up in coronaryarteries.

What is claimed is:
 1. A method for preventing plaque build-up in acoronary artery, comprising: providing an electrical field generatingdevice, wherein providing the electrical field generating deviceincludes inserting an implant in a patient's body, connecting theimplant to a lead, and extending the lead within the patient's bodyadjacent the coronary artery; and generating an electrical field in thecoronary artery to prevent plaque build-up in the coronary artery. 2.The method according to claim 1, wherein the lead includes an electrodepatch, and extending the lead includes positioning the electrode patchepicardially on a heart adjacent to the coronary artery.
 3. The methodaccording to claim 1, wherein extending the lead includes inserting thelead into a vein adjacent the coronary artery, and generating theelectric field includes producing an electric field of sufficientstrength to pass through walls of the vein and the coronary artery toprevent plaque from adhering to the wall of the coronary artery.
 4. Themethod according to claim 1, wherein inserting the implant includessensing a heart rhythm of the patient's heart, and generating theelectrical field includes outputting a non-excitatory electrical fieldsuch that the electrical field does not interfere with the heart rhythm.5. The method according to claim 4, wherein generating the electricalfield includes generating the field after heart depolarization.
 6. Themethod according to claim 5, wherein generating the electric fieldincludes periodically producing the electric field and spacing theelectrical fields about 10 seconds apart.
 7. The method according toclaim 1, wherein connecting the implant to a lead includes connectingthe implant to at least two electrodes on the lead such that theelectrical field is generated between the at least two electrodes. 8.The method according to claim 1, wherein connecting the implant to alead includes connecting the implant to at least two leads each havingone electrode, and spacing the two electrodes apart from each other suchthat the electrical field generated between the two electrodes reducesplaque build-up in the coronary artery.
 9. The method of claim 1,wherein generating the electrical field includes generating theelectrical field during the refractory period at a higher strength andgenerating the electrical field during the non-refractory period at alower strength.
 10. An apparatus for preventing plaque build-up in acoronary artery, comprising: a heart rhythm sensing unit; an electricalfield generating device connected to the heart rhythm sensing unit, theelectrical field generating device produces an electrical field thatdoes not interfere with the heart rhythm; and a lead unit connected tothe electrical field generating device, the lead unit producing theelectrical field adjacent the coronary artery to reduce plaque build-upin the coronary artery.
 11. The apparatus according to claim 10, whereinthe electrical field generating device includes an implantable housing,a power source within the housing, and electrical field generatingcircuitry connecting the power source to the lead unit.
 12. Theapparatus according to claim 10, wherein the lead unit includes anelectrode patch positioned epicardially on the heart.
 13. The apparatusaccording to claim 10, wherein the lead unit is an intracardial lead andis positioned in a vein adjacent the coronary artery.
 14. The apparatusaccording to claim 10, wherein the lead unit includes two leads eachhaving an electrode thereon, the electrodes being spaced from oneanother in a body with the coronary artery therebetween, and the leadunit flowing current between the two leads to create the electricalfield in the coronary artery and prevent plaque build-up in the coronaryartery.
 15. The apparatus according to claim 14, wherein one of the twoleads is positioned in an anterior vein and a second of the two leads ispositioned in a lateral vein, and the electrical field is anon-heart-excitatory signal passing through a left marginal artery andan anterior interventrical artery.
 16. The apparatus according to claim10, wherein the electrical field generating device produces anelectrical field less than is needed to capture the cardiac tissue. 17.The apparatus according to claim 16, wherein the electrical fieldgenerating device produces an electrical field less than every 10seconds.
 18. The apparatus according to claim 10, wherein the electricalfield generating device produces an electrical field after adepolarization wave in the heart.
 19. The apparatus according to claim10, wherein the electrical field generating device includes a controllerand therapy circuits for providing heart rhythm management signals to aheart.
 20. The apparatus according to claim 10, wherein the electricalfield generating device produces an electrical field during a refractoryperiod of the hear rhythm.